1. Field of the Invention
Aspects of the present invention relate to a battery management system. More particularly, aspects of the present invention relate to a battery management system used in a vehicle using electrical energy.
2. Description of the Related Art
Vehicles with an internal combustion engine using gasoline or diesel have caused serious air pollution. Accordingly, various attempts to develop electric or hybrid vehicles have recently been made to reduce such air pollution.
An electric vehicle uses an electric motor operating by electrical energy output from a battery. As the electric vehicle generally uses a battery formed of at least one battery pack including a plurality of rechargeable/dischargeable (or secondary) cells, there is merit in that the electric vehicle generates no emission gases and produces less noise.
The term “hybrid vehicle” commonly refers to a gasoline-electric hybrid vehicle that uses gasoline to power an internal-combustion engine and a battery to power an electric motor. Recently, hybrid vehicles using an internal-combustion engine and fuel cells and hybrid vehicles using a battery and fuel cells have been developed. The fuel cells directly produce electrical energy through a chemical reaction between hydrogen and oxygen, which are continuously provided thereto.
Since battery performance directly affects the performance of the vehicle using electrical energy, it is required that each battery cell has great performance. Also, a battery management system (BMS) is necessary to measure a voltage and a current of the overall battery to efficiently manage charging/discharging operations of each battery cell therein.
In general, the battery management system uses a data table, in which a relationship between an open circuit voltage (OCV) and a state of charge (SOC) is stored, to estimate the SOC therefrom. In this case, it is required to precisely measure the OCV so as to precisely calculate the SOC.
When the battery is in the no-load state after being consistently charged or discharged, the OCV may not be precisely measured since polarization and internal resistance in the battery is generated. A length of time necessary to correct the polarization is required to precisely measure the OCV. However, it is difficult to guarantee such a time when a hybrid vehicle is driven. Accordingly, an error in measuring the OCV measured in a short time or before the correction of the polarization may cause an error in the calculation of the SOC.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.